QCAD up to version 2.0.5.0 is open source (the binary you have found is probably compiled from sources of that version). Note that the Sourceforge project is a community effort, independent of RibbonSoft and not supported by us.

> Another thing that disadvantages potential contributors is the releasing scheme.
> When new version of QCad will be released as Community Edition, what happened
> with a contributor's patch?

Well, even worse: for example, I tried to contribute the auto-save patch about 3
years ago, when the community-license version has already been at 2.0.5 (but wasn't
as outdated as it is now). I never got any feedback, and from reading the release
notes it seems that even the current commercial version still doesn't implement such
a feature. This is disgusting in two ways: as a potential contributor, I don't stand a
chance to contribute something to the current development version, so I don't even
know whether my contribution would still be applicable there with little or no effort.
If it's not applicable (as might be the case here), the effort for the QCAD developers
to integrate it would probably be the same as the effort to write it from scratch, so
it will never be integrated then.

As a potential customer for the commercial version, the lack of a feature I implemented
years ago in my copy of the community version, of course, makes me think twice
whether I'd really like to buy it.

I don't have a real solution, and I really don't want to complain: QCAD is by far the
best (mechanical) CAD tool around here on my FreeBSD system, and I'm thankful
it does exist. However, the current community license model really doesn't attract
much contributions (and given the zero response to my previous contribution, I'm
not very motivated to contribute anything else by now, even though you can find
code contributions from me scattered throughout the Internet in many programs).

OTOH, I understand that without people even attempting to contribute, there's also
zero motivation for the QCAD developers to change the current way.

dl8dtl: Unfortunately, we simply don't have any resources to work on the community edition, doing releases, looking into patches, etc.

We hope that the situation will improve with the release of QCAD 3. QCAD 3 will likely not be open source but offer such a powerful scripting interface that you can implement almost any thinkable tool or extension (e.g. auto save) through scripts that can be easily downloaded and installed by others.

We hope that this model will create a certain dynamics without too much involvement from our side, so we can focus on our core business.

The only drawback I'm seeing with that is that QCad and QCad will then no longer be
the same:

Suppose I've been using the community version for quite some time (which I did now),
and I'm basically happy with it but would now like to obtain a copy of the commercial
version, basically in order to support your organization. The QCad product I'm about
to buy will then be something fairly different than the one I'm used to, a new learning
curve, new features, new UI, things are likely no longer there the way I'm used to.
In short: it's a different product then.

But OK, if version 3 is out, I might have a look at the downloadable demo to see how
it looks like, and how it's working.